Power Quality and Voltage Stability of Power Systems with a large share of Distributed Energy Resources

The main objective of this research is to model and characterize power systems with a large share of distributed energy resources. The effect of integrating distributed energy resources such as wind farms, photovoltaic arrays, fuel cell stacks and micro-hydroelectric generators on the power quality and voltage stability of power systems is investigated and characterized. A comprehensive power system model was developed in Matlab/Simulink environment. Stand-alone and grid-connected models of distributed energy resources were developed and integrated into the system under investigation. Several characteristics such bus voltage profiles, voltage transients, power flow, and total harmonic distortion are captured and investigated. The integration of Flexible Alternating Current Transmission Systems (FACTS) devices such as Static Synchronous Series Compensator (SSST), Unified Power Flow Controller (UPFC), Static VAR Compensator (SVC), and Static Compensator (STATCOM) into power systems was also studied. Models of common FACTS devices were developed and integrated into the power system model. The effect of installing FACTS devices on the power quality and voltage stability of power systems with a significant component of distributed energy resources was investigated. Power system characteristics with and without FACTS devices were determined and investigated. From the simulation results, it is observed that there is a significant improvement in the power quality by integrating FACTS device. Future research into the feasibility and optimal location of FACTS devices to improve power system performance and operation will be needed

Application of STATCOM for improved dynamic performance of wind farms in a power grid

This thesis investigates the use of a Static Synchronous Compensator (STATCOM) along with wind farms for the purpose of stabilizing the grid voltage after grid-side disturbances such as a three phase short circuit fault, temporary trip of a wind turbine and sudden load changes. The strategy focuses on a fundamental grid operational requirement to maintain proper voltages at the point of common coupling by regulating voltage. The DC voltage at individual wind turbine (WT) inverters is also stabilized to facilitate continuous operation of wind turbines during disturbances --Abstract, page iii

Implementation of grid-connected wind energy during fault analysis using moth flame optimization with firebug swarm optimization

In modern trends, the voltage profile has become increasingly critical when incorporating wind turbine energy sources because of changes in fault ride-through capabilities throughout voltage reaction. Ripple, voltage magnitude changes, and injected harmonics due to conversion switches are power quality issues for grid-integrated doubly fed induction generators (DFIG) wind sources. In this study, FACTS (flexible alternating current transmission system) devices like the static VAR compensator (SVC), thyristor controlled series compensator (TCSC), unified power flow controllers (UPFC), and static synchronous compensators (STATCOM) are used to stabilise wind energy with DFIGs. The simulation test cases using MATLAB also analyse three lines to ground fault (LLL-G) of fault measures, which showed a 9 MW that transferred to utility grid. Therefore, it is suggested to inject or absorb reactive power to stabilise the system using moth flame optimization with firebug swarm optimization (MFO-FSO). The simulation results clearly demonstrate that the proposed MFOFSO based STATCOM devices outperform the current nonlinear generalized predictive control based STATCOM, which only achieves 0.9815 per unit voltage stability, by achieving a higher voltage profile of 0.9925 per unit voltage stability with a reactive power injection of 1.82 MVAR.Peer ReviewedPostprint (published version

Review of trends and targets of complex systems for power system optimization

Optimization systems (OSs) allow operators of electrical power systems (PS) to optimally operate PSs and to also create optimal PS development plans. The inclusion of OSs in the PS is a big trend nowadays, and the demand for PS optimization tools and PS-OSs experts is growing. The aim of this review is to define the current dynamics and trends in PS optimization research and to present several papers that clearly and comprehensively describe PS OSs with characteristics corresponding to the identified current main trends in this research area. The current dynamics and trends of the research area were defined on the basis of the results of an analysis of the database of 255 PS-OS-presenting papers published from December 2015 to July 2019. Eleven main characteristics of the current PS OSs were identified. The results of the statistical analyses give four characteristics of PS OSs which are currently the most frequently presented in research papers: OSs for minimizing the price of electricity/OSs reducing PS operation costs, OSs for optimizing the operation of renewable energy sources, OSs for regulating the power consumption during the optimization process, and OSs for regulating the energy storage systems operation during the optimization process. Finally, individual identified characteristics of the current PS OSs are briefly described. In the analysis, all PS OSs presented in the observed time period were analyzed regardless of the part of the PS for which the operation was optimized by the PS OS, the voltage level of the optimized PS part, or the optimization goal of the PS OS.Web of Science135art. no. 107

Grid Strength Assessment Trough Q-V Modal Analysis and Maximum Loadability of a Wind-Dominated Power System Using P-Q Regions

Climate change is a menace to the existence of the world and policymakers are trying totackle this phenomenon by deploying large-scale wind farms into their grids. Among them, wind energy shows a promising future to substitute the traditional power plants. However, the deployment of these wind farms into the grid is not a panacea that does not pose any challenges to the grid operators. Keeping the power system voltage stable while considering the strength of the transmission grid is among the major challenges facing by the transmission system operators. Amid normal operation and fault conditions, wind farms should help the grid in reactive power supply according to the grid codes to ride through the fault. In doing so, during fault conditions or heavy loading conditions, the voltage of the power system will not deteriorate. A wind farm, most of the time, is incapable to meet the grid codes requirements without reactive power support. For the compensation of the reactive power deficit, FACTS devices are extensively used. The most popular FACTS devices used by electric utilities are, STATCOM, SVC, SSSC, TCSC, and UPFC. In this work, attention is given to the amelioration of transient stability in wind-dominated power systems via STATCOM and SSSC. Furthermore, a systematic approach to locate large wind power plants to an existing transmission grid is developed by combining the QV-modal analysis, Q-V curves, and P-Q method. The steady-state voltage stability at different wind power penetration levels is investigated while considering the weakest and the strongest region of the power system. The P-Q region method is used to size the wind farm in each scenario. The reliability of the system is verified from the worst contingencies with the wind farm connected at the most vulnerable bus of the system in reactive power capability. The system considered for testing is the modified IEEE 14 bus system

NEW APPROACHES FOR VERY SHORT-TERM STEADY-STATE ANALYSIS OF AN ELECTRICAL DISTRIBUTION SYSTEM WITH WIND FARMS

Distribution networks are undergoing radical changes due to the high level of penetration of dispersed generation. Dispersed generation systems require particular attention due to their incorporation of uncertain energy sources, such as wind farms, and due to the impacts that such sources have on the planning and operation of distribution networks. In particular, the foreseeable, extensive use of wind turbine generator units in the future requires that distribution system engineers properly account for their impacts on the system. Many new technical considerations must be addressed, including protection coordination, steady-state analysis, and power quality issues. This paper deals with the very short-term, steady-state analysis of a distribution system with wind farms, for which the time horizon of interest ranges from one hour to a few hours ahead. Several wind-forecasting methods are presented in order to obtain reliable input data for the steady-state analysis. Both deterministic and probabilistic methods were considered and used in performing deterministic and probabilistic load-flow analyses. Numerical applications on a 17-bus, medium-voltage, electrical distribution system with various wind farms connected at different busbars are presented and discusse

Future work on harmonics : some expert opinions part I : wind and solar power

A workshop on power system harmonics was organized in Stockholm in January 2014. On the agenda was among others a discussion on what are the main issues on harmonics at the moment and in the near future. The results of this discussion are summarized in this paper and some of the issues are discussed in more detail in this paper and in its companion paper. This paper discusses emission from wind and solar power as well as advantages and disadvantages of active and passive filters

STATCOM and SVC with Wind Turbines

The large wind parks are the feasible solution in order to generate clean energy compared with conventional power plants. Therefore, the interest in the Wind Energy Conversion System (WECS) is quickly increasing to reduce the fossil fuels dependencies. While the penetration of the WECS increases into the grid, many of the technical challenges have appeared. Low voltage Ride Through (LVRT) is the new requirement which needs to be fulfill when the amount of wind power generation increases, to be able to guarantee the power system reliability and stability. The voltage dips that result from faults in the grid can lead to a loss generation unit. According to the LVRT, WTs are required to be always connect during the fault, and to support the power system by supplying reactive power to ensure grid stability. The main purpose of the thesis was to investigate that how the LVRT of Doubly Fed Induction Generator (DFIG) based Wind Turbine Generator (WTG) can be enhanced using shunt connected Flexible AC Transmission System (FACTS) devices Static Synchronous Compensator (STATCOM) and Static Var Compensator (SVC). The theoretical background related to the LVRT enhancement using STATCOM and SVC is performed, and results are verified by the simulation model. This thesis is constructed in 5 Chapters, Chapter 1 gives an overview about the problems related to wind power. Chapter 2 explains the different grid codes and different topologies of the wind turbine technologies. Chapter 3 explains the working principle, construction and applications of the STATCOM and SVC. A comprehensive comparison between the STATCOM and SVC is also explained in this chapter. The operation of DFIG wind turbine during voltage dip is analyzed by using the simulation model in the next Chapter. In the first case, the effect of a three-phase fault on the power system was analyzed without using any compensation device. The LVRT requirements were not fulfilled without any compensation device. Therefore, in the second case, SVC was added in the model. Some improvement was observed in this case, but it was not enough to fulfill very strict LVRT requirements such as German Grid Codes (GGCs).Therefore, in the third case, SVC is replaced by STATCOM to meet the LVRT requirement of GGCs. In the last case, three different ratings of STATCOM were utilized to see the effect on the grid voltage and reactive power support by STATCOMs. The key findings of this thesis work are reported by Chapter 5